Molding method and molding device utilizing ultrasonic vibration and optical lens

ABSTRACT

A molding method is provided which can further improve transferability and further reduce strain and which is suitable for molding of a product with high accuracy and high quality. The molding method in which a resin material is filled into a cavity formed in a mold and pressurized to mold a product in a predetermined shape, and the method comprises: preparing the mold having a product cavity to mold the product made of a resin, a dummy cavity to mold a dummy product, and a runner by which the product cavity and the dummy cavity are connected; filling the resin material into the product cavity and supplying the resin material to at least part of the dummy cavity; and applying ultrasonic vibration to the resin material in the dummy cavity at predetermined timing.

TECHNICAL FIELD

The present invention relates to a molding technique comprising fillinga resin material into a cavity formed in a mold and compressing it toobtain a product in a predetermined shape. More particularly, it relatesto a molding method using ultrasonic vibration to mold optical lenses(such as spectacle lenses) with high accuracy and high quality; amolding machine; and the optical lenses.

BACKGROUND ART

A technique has heretofore been known to manufacture products such asoptical lenses requiring high accuracy by injection molding (e.g., referto description of a specification and drawings of Japanese PatentPublication Laid-open No. 9-272143, and description of a specificationand drawings of Japanese Patent Publication Laid-open No. 9-277327).

However, when, for example, the optical lenses are injection-molded byuse of a method described in Japanese Patent Publication Laid-open No.9-272143, there is a problem that a resin material contracts when it iscooled and solidified in a cavity, which deteriorates transferability ofa mold to the product and makes it impossible to obtain a desiredaccuracy. Thus, in conventional injection molding, the cavity is formedin such a manner as to add a correction value to a target power inconsideration of the contraction (strain) during cooling andsolidification and the deterioration of transferability, so that theoptical lens with the target power can be obtained when it is taken outfrom the cavity. For example, in order to mold an optical lens having atarget power of −4.0 diopters (D), the cavity is formed to suit to ashape of the optical lens having a power of “−4.0 (D)+α” in which thecorrection value α is added. However, this method still has a problemthat the molding of the optical lens with high accuracy is difficult.

Furthermore, in order to improve the transferability, an injectionpressure during the molding may be increased, but if the injectionpressure is increased, another problem occurs wherein a molding machinewith high clamping force is needed and highly rigid mold is required,which leads to the increase of costs. Moreover, to suppress the strain,highly accurate mold temperature adjustment is carried out and coolingtime is extended to reduce the strain and to improve the transferabilityas described in Japanese Patent Publication Laid-open No. 9-277327, butthis manner causes such a problem that a molding cycle is too long,which is not suitable for practical application.

In addition to the above, various proposals have been made to obtain thehighly accurate optical lenses in an injection molding machine (e.g.,refer to an abstract and drawings of Japanese Patent PublicationLaid-open No. 7-100878).

In a technique described in Japanese Patent Publication Laid-open No.7-100878 mentioned above, a movable mold is provided with a first punch7 which can plunge into a plate-like cavity and can vibrate in a plungedirection, and a fixed mold is provided with a second punch which isdisposed opposite to the first punch so as to sandwich the plate-likecavity and which can follow the first punch and can synchronize with thesame. Moreover, a plunge surface of at least one of the punches isprovided with a molding shape portion of a product section 5 to betransferred to a product surface, so that the compression,pressurization, punching, etc. of the product section 5 are performedwhile both the punches are being vibrated during an injection moldingprocess.

This technique is effective to reduce internal strain and to improve thetransferability, but has a problem that it still cannot obtainsufficient effects when optical lenses with higher accuracy are molded.

This invention has been attained in view of the foregoing problems, andits objects are to provide a method of molding a product usingultrasonic wave which can improve the transferability during molding andfurther reduces strain and which is suitable to a product such as anoptical lens requiring high accuracy and high quality, and to providethe optical lens such as a spectacle lens molded by a molding machine toimplement the molding method and in accordance with this molding method.

DISCLOSURE OF THE INVENTION

As a result of dedicated studies, the inventors of the present inventionhave found out that ultrasonic vibration is applied to a resin materiallocated outside a cavity of a product when the resin material is filledinto the cavity to mold the product, and this allows improvement intransferability and a reduction in strain.

That is, a first aspect of the present invention is directed to amolding method using ultrasonic vibration in which a resin material in amolten state is filled into a cavity of a mold and cooled down to obtaina product in a predetermined shape, the method comprising preparing themold having a product cavity to mold the product, a dummy cavity to molda dummy product, and a runner by which the product cavity and the dummycavity are connected; filling the resin material into the product cavityand supplying the resin material in the molten state to at least part ofthe dummy cavity; and applying the ultrasonic vibration to the resinmaterial in the dummy cavity at predetermined timing.

A second aspect of the present invention is directed to a molding methodusing ultrasonic vibration in which a resin material in a molten stateis filled into a cavity of a mold and cooled down to mold a product in apredetermined shape, the method comprising preparing the mold having aplurality of product cavities to mold the products, a runner by whichthe product cavities are connected to each other, and a resin pitprovided at a halfway part of the runner; supplying the resin materialto the resin pit and filling the resin material into all of theplurality of product cavities; and applying the ultrasonic vibration tothe resin material in the resin pit at predetermined timing.

According to these methods of the present invention, the ultrasonicvibration is applied to the resin material in the dummy cavity or theresin pit so that the resin material in the dummy cavity or the resinpit may be heated and molten and a pumping effect may work to pressurizethe resin material in the product cavity, and it is thus speculated thatthe strain of the product (product such as an optical lens) molded inthe product cavity is reduced and the transferability is improved.

As in the present invention, application timing of the ultrasonicvibration is advantageously after the supply of the resin material to atleast part of the dummy cavity or the resin pit is started and while theresin material in the runner has a predetermined viscosity. Theultrasonic vibration may also be applied while a compressed state ismaintained after the resin material is filled into the product cavityand compressed, as in the present invention.

Furthermore, as in the present invention, the ultrasonic vibration isadvantageously applied so that an amount of the resin material flowinginto the product cavity from the dummy cavity and air gaps other thanthe product cavity may be in a range of 0.1% by volume to 5% by volumeof the resin material filled into the product cavity.

Moreover, as in the present invention, the ultrasonic vibration isadvantageously applied immediately after the filling of the resinmaterial is started and until a gate in communication with the productcavity is sealed, and as in the present invention, a nozzle of a moldingmachine to supply the resin material to the mold is advantageouslyclosed immediately after the filling of the resin material is completed.The present invention is suitable for molding of the optical lensrequiring high accuracy and high quality, and particularly suitable formolding of a spectacle lens. In addition, when the spectacle lens ismolded, a surface treatment is preferably implemented after molding, asin the present invention.

The method described above can be implemented by a molding machine ofthe present invention.

In a configuration of the present invention, a molding machine isprovided in which a resin material in a molten state is filled into acavity of a mold and cooled down to obtain a product in a predeterminedshape, and the molding machine comprises: a mold having a product cavityto mold the product, a dummy cavity to mold a dummy product, and arunner by which the product cavity and the dummy cavity are connected;ultrasonic wave application means for applying ultrasonic vibration tothe resin material in the dummy cavity; and control means forcontrolling application timing of the ultrasonic vibration by theultrasonic wave application means.

According to this configuration, the ultrasonic vibration is applied tothe dummy cavity to mold the dummy product at predetermined timing,thereby allowing improvement in transferability of the product molded inthe product cavity and a reduction in strain.

Alternatively, in a configuration of the present invention, a moldingmachine is provided in which a resin material in a molten state isfilled into a cavity of a mold and cooled down to mold a product in apredetermined shape, and the molding machine comprises: a mold having aplurality of product cavities to mold the products, a runner by whichthe product cavities are connected to each other, and a resin pitprovided at a halfway part of the runner; ultrasonic wave applicationmeans for applying ultrasonic vibration to the resin material in theresin pit; and control means for controlling application timing of theultrasonic vibration by the ultrasonic wave application means.

In this case, predetermined ultrasonic vibration is applied to the resinpit, thereby allowing improvement in the transferability of the productmolded in the product cavity and a reduction in strain.

The application timing of the ultrasonic vibration by the control meansmay be after supply of the resin material to at least part of the dummycavity or the resin pit is started and while the resin material in therunner has a predetermined viscosity. The timing may also be when acompressed state is maintained after the resin material is filled intothe product cavity and compressed.

The mold may have a sprue in communication with the runner. Further, theresin pit may be formed at the midpoint of the runner. Still further,the resin pit may be formed at a part where the sprue communicates withthe runner.

The molding machine of the present invention is suitable for the moldingof the optical lens (including the spectacle lens) requiring highaccuracy and high quality.

According to the present invention, the transferability is significantlyimproved and the strain is extremely reduced in a simple manner withoutincreasing pressure during injection molding and making a highlyaccurate mold temperature adjustment and cooling time adjustment,thereby making it possible to mold a product with high accuracy and highquality, for example, the optical lens such as the spectacle lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a mold of a molding machine according to afirst embodiment of the present invention, wherein (a) is a schematicsectional view to explain a configuration of the mold, and (b) is a planview of a movable mold in which cavities are formed;

FIG. 2 is a diagram showing a procedure of molding a product in thefirst embodiment;

FIG. 3 is a diagram showing the mold of the molding machine according toa second embodiment of the present invention, wherein (a) is a schematicsectional view to explain the configuration of the mold, and (b) is aplan view of the movable mold in which the cavities are formed;

FIG. 4 is a diagram showing a procedure of molding the product in thesecond embodiment;

FIG. 5 is a flow diagram for spectacle lens molding in the secondembodiment; and

FIG. 6 is a perspective view showing a modification of a resin pit.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will hereinafter bedescribed in detail with reference to the drawings.

FIG. 1 is a diagram showing a mold of a molding machine according to afirst embodiment of the present invention, wherein (a) is a schematicsectional view to explain a configuration of the mold, and (b) is a planview of a movable mold in which cavities are formed.

[Scope of Molding]

The “molding” to which a molding method of the present invention isapplicable includes injection molding of a resin material injected intothe cavity of the mold to mold a product in a predetermined shape, andalso includes injection compression molding in which the resin materialin the cavity is pressurized after the resin material is filled into thecavity.

[Molding Material]

As one example of a material for molding used in the present invention,it is possible to use a thermoplastic resin or a thermoplastic resincomposition in which organic matter or inorganic matter is mixed intothe thermoplastic resin.

[Configuration of the Mold]

A mold 10 comprises a fixed mold 11 and a movable mold 12. In themovable mold 12, there are formed a product cavity 17 to mold a productin a predetermined shape (such as an optical lens), and a dummy cavity18 to mold a dummy product. Further, the product cavity 17 is coupled tothe dummy cavity 18 by a runner 19.

In the fixed mold 11, a sprue 13 is formed in a protruding manner whichsupplies the resin material to the runner 19. An unshown nozzle of themolding machine is pressed against the sprue 13, and the resin materialinjected/supplied from the nozzle is supplied to the product cavity 17and the dummy cavity 18 via the sprue 13 and the runner 19.

Furthermore, a storage section 11 a is formed at a positioncorresponding to the dummy cavity 18, and the storage section 11 a isprovided with a vibrator 15. A tip of this vibrator 15 is adapted tocontact the resin material supplied to the dummy cavity 18 via a core 15a during clamping.

An ultrasonic vibrator 16 is attached to a side surface of the vibrator15, and vibration of this ultrasonic vibrator 16 is applied to thevibrator 15.

[Vibration Application Means]

When the ultrasonic vibrator 16 vibrates, this vibration is transmittedto the vibrator 15, and will be vibration in a diametrical direction tobe applied to the mold 10.

It is to be noted that the vibrator 15 may apply vibration without nodesto the resin material by actuation of the ultrasonic vibrator 16. Inthis case, the core 15 a which applies the vibration of the vibrator 15to the dummy cavity 18 has about the same outside diameter as an insidediameter of the dummy cavity 18.

Although not specifically shown in the drawing, the ultrasonic vibrator16 is coupled to the vibrator 15 by a bar-shaped vibrating horn having apredetermined length, and the vibration of the ultrasonic vibrator 16may be transmitted to the vibrator 15 via the vibrating horn.

The vibrator 15 and the ultrasonic vibrator 16 can be formed using ametal, ceramics, graphite or the like, but it is preferably formed by ametal such as an aluminum alloy, a titanium alloy or the like havingsmall transmission loss if the transmission loss of the ultrasonicvibration is considered.

The vibrator 15 needs to be fixed so as to cause the least interfere toresonance. For the vibrator 15 not to have the nodes of the vibration, aflange (not shown) is advantageously provided in the ultrasonic vibrator16, and this flange is fixed to the vibrator 15 by a bolt or the like.

The ultrasonic vibrator 16 is vibrated by an unshown ultrasonicoscillator. Since the ultrasonic oscillator responds to a change in aresonance frequency due to a temperature change or an acoustic loadchange due to a change in a molding condition, the oscillator ispreferably an automatic frequency follow-up type oscillator with anamplitude control circuit.

Furthermore, when a necessary ultrasonic output does not reach arequired value using one vibrator, a plurality of ultrasonic vibrators16 can be used to the vibrator 15. In that case, a necessary number ofultrasonic vibrators 16 having the same vibration characteristic isprepared, and they may be attached onto an outer peripheral surface ofthe vibrator 15 at equal intervals.

Moreover, a known ultrasonic output synthesizer can be used to applyhigher ultrasonic vibration. In this case, for example, the ultrasonicvibrators 16 are bonded to sides of a vibrating plate formed into apolygonal shape (an octagon or a polygonal with more sides) so as not toimpair frequency characteristics, and these ultrasonic vibrators 16 arevibrated in phase, and their outputs are collected to a central portion,so that the vibration may be applied to the vibrator 15 from a resonancebar provided at the central portion.

[Ultrasonic Oscillator]

As the ultrasonic oscillator (not shown) which applies the ultrasonicvibration to the resin material in the dummy cavity 18, it is possibleto use an ultrasonic oscillator known from, for example, Japanese PatentPublication Laid-open No. 11-262938 disclosed in accordance with anapplication of the present applicant.

[Vibration Frequency]

A vibration mode of the ultrasonic vibration oscillated from theultrasonic oscillator may be such that it can apply predeterminedvibration (amplitudes and a number of vibrations) to the resin material,and the vibration may be one of longitudinal vibration, lateralvibration, diametrical vibration and torsional vibration, or acombination of these vibrations.

A frequency of the ultrasonic vibration is preferably 1 KHz to 1 MHz,and it is preferable to select from a range of 10 KHz to 100 KHz for thevibration to effectively act on the resin material during molding.

Furthermore, the maximum amplitude of the ultrasonic vibration isdetermined by fatigue strength of a material constituting the mold 10.For example, when the mold 10 is made of an SUS-based material, themaximum amplitude is advantageously about 20 μm, about 40 μm forduralumin, and 100 μm for the titanium alloy.

[Application Timing of the Ultrasonic Vibration]

The application timing of the ultrasonic vibration is an optional timewhen a gate of the product cavity 17 is sealed with the cooled resinmaterial immediately after the injection of the resin material isstarted. It is to be noted that the unshown nozzle of the moldingmachine is advantageously closed (shut) immediately after filling of theresin material is completed while the ultrasonic vibration is beingapplied.

Furthermore, the ultrasonic vibration is preferably applied so that anamount of the resin material flowing from the dummy cavity 18 and airgaps other than the product cavity 17, in this embodiment, from thedummy cavity 18, the runner 19 and the like to the product cavity 17 maycorrespond to 0.1% by volume to 5% by volume, preferably 0.2% by volumeto 2% by volume of a total capacity of the product cavity 17.

Time to reach this amount depends on a size of a product to be produced,but when the product is, for example, a spectacle lens, the time can beabout 30 seconds to 60 seconds from the filling start of the resinmaterial. In this case, the time is about 60 seconds when the spectaclelens is large, while it is about 30 seconds when the spectacle lens issmall.

A procedure of molding the optical lens by the molding machine using themold configured as described above will be described referring to FIG.2.

First, the movable mold 12 is moved toward the fixed mold 11 to performclamping, as shown in FIG. 2(a).

After the clamping is completed, a resin material M is supplied from thesprue 13 to the product cavity 17 through the runner 19. At this moment,part of the resin material M is also supplied to the dummy cavity 18through the runner 19.

Then, as shown in FIG. 2(b), the ultrasonic oscillator is drivenimmediately after the filling of the resin material M is started,thereby applying the ultrasonic vibration from the vibrator 15 to thedummy cavity 18.

In this case, a pressurized state is still retained for a certain time(e.g., 45 seconds) after the filling of the resin material M into theproduct cavity 17 and the dummy cavity 18 is completed, and during thisperiod, the ultrasonic vibration may be continuously applied. Further,after the filling of the resin material into the product cavity 17 andthe dummy cavity 18 is completed, the nozzle is closed and theultrasonic vibration may be applied while the resin is being pressurizedwithout holding pressure. It is to be noted that in the latter case, itis preferable to continue applying the ultrasonic vibration for acertain time (e.g., 60 seconds) in accordance with the size of theproduct.

By applying the ultrasonic vibration, the resin material in the dummycavity 18 is heated and molten, and caused to flow into the productcavity 17. (This is called “pumping effect” in this specification.)Thus, the resin material M filled into the product cavity 17 ispressurized, thereby allowing strain to be reduced and transferabilityto be improved.

At the instant when the resin material M in the product cavity 17 iscooled down and the gate of the product cavity 17 is thus cooled downand solidified, the application of the ultrasonic vibration is stopped,and the movable mold 12 is moved in a direction away from the fixed mold11 to open the mold as shown in FIG. 2(c), thus taking out a product P.Since a product portion Pa (portion to be the optical lens) and a dummyproduct portion Pb are formed into the product P that has been takenout, the product portion Pa is only separated in a next process.

Second Embodiment

FIG. 3 is a diagram to explain a mold of a molding machine according toa second embodiment of the present invention, wherein (a) is a schematicsectional view to explain a configuration of the mold, and (b) is a planview of a movable mold in which cavities are formed.

It is to be noted that formation of a spectacle lens as an optical lenswill be described by way of example in the second embodiment.

A mold 20 comprises a fixed mold 21 and a movable mold 22. In themovable mold 22, there is formed a plurality of product cavities 27 tomold a product. The product cavities 27 are coupled by a runner 29. Aresin material supplied via a sprue 23 formed in the fixed mold 21 isfilled into the product cavities 27 via the runner 29, thus molding aproduct in a predetermined shape.

A resin pit 28 is formed at the midpoint of the runner 29, in thisembodiment, at a part where the sprue 23 communicates with the runner29, and a predetermined amount of the resin material is retained in theresin pit 28 when the product (spectacle lens) is molded. A capacity ofthis resin pit 28 is advantageously 3% or more with respect to acapacity of the product cavities 27, and preferably 10% or more.

However, a amount of the lost resin material increases over 60%, whichis not preferable in practical use, and thus, it is preferably within 3%to 60%, and more preferably, within 10% to 40%.

In the movable mold 22, a through-hole 22 b in communication with theresin pit 28 is formed in the same direction as a forward/backwardmoving direction of the movable mold 22, and part of a vibrator 25 isinserted in the through-hole 22 b. Further, a tip 25 a of the vibrator25 forms a bottom of the resin pit 28.

The vibrator 25 is supported by a support member 22 a attached to themovable mold 22 (opposite to the fixed mold 21). Further, a ultrasonicvibrator 26 is attached to a side surface of the vibrator 25.

It is to be noted that the vibrator 25, the ultrasonic vibrator 26, anultrasonic oscillator and other basic configurations to apply vibrationare the same as those in the first embodiment, and further detaileddescription thereof is not given.

The application timing of the ultrasonic vibration may be similar tothat in the first embodiment, or may be simultaneous with injection.Moreover, as in the first embodiment, the ultrasonic vibration ispreferably applied so that an amount of the resin material flowing fromthe resin pit 28 and the runner 29 to the product cavities 27 maycorrespond to 0.1% by volume to 5% by volume, preferably 0.2% by volumeto 2% by volume of a total capacity of the product cavity 27.

Furthermore, a method of molding such a spectacle lens is realized byusing the molding method and the molding machine of the presentinvention as described above, but more preferably, a convex surface ofthe spectacle lens further serves as a fixed mold, and the ultrasonicvibration is applied to that fixed mold.

Still further, it is preferred to shut a nozzle rather than holdpressure after the injection and filling of the resin material insuppressing residual strain, and moreover, greater clamping forcereduces the strain and approximates designed power of the lens. When thepressure is held, the residual strain will decrease if the clampingforce is reduced.

Next, there will be described, together with a flowchart of FIG. 5, apreferred procedure of molding the spectacle lens having a meniscusshape by use of a mold shown in FIG. 4(a) to FIG. 4(c) in the secondembodiment.

It is to be noted that FIG. 4(a) to FIG. 4(c) illustrate how to drivethe movable mold 22 and the fixed mold 21 of the mold of the moldingmachine, and also illustrate arrangements of a mold construct (23, 27,28, 29) having the product cavity, the resin pit, the runner and thesprue, and of the vibrator 25.

First, a mold is selected in accordance with the kind of lens to bemolded.

A mold is prepared which has the product cavity whose thickness islarger in a central portion than in a peripheral portion in a case ofmolding a positive-power lens, while a mold is prepared which has theproduct cavity whose thickness is smaller in the central portion than inthe peripheral portion in a case of molding a negative-power lens.

In ST (step) 1, measurement is made. A raw resin put into a hopper (notshown) of an injection apparatus is plasticized, and the plasticizedmolten resin is introduced into an injection cylinder unit and measuredtherein. Here, the amount of the resin material is measured which isnecessary for the mold construct having the product cavity, the resinpit, the runner and the sprue. It is to be noted that the measurement isgenerally operated independently in a cooling process described later ina molding cycle during continuous molding after an initial operation.

In ST2, a resin compression condition is set. This is done to adjust theclamping force depending on characteristics (such as a lens shape andlens power) of the lens to be molded in order to apply proper pressureto the resin in the product cavity in advance. Needless to say, thisresin compression condition is changed depending on resincharacteristics, and the resin characteristics are considered in allmolding conditions.

In ST3, ST4, the mold is closed on a parting line, and the capacity ofthe product cavity is set. That is, the movable mold is carried forwardto a preset product cavity capacity setting position. At this point, thecapacity (thickness) of the product cavity is in a state made largerthan the capacity (thickness) of the lens to be molded, that is, thethickness of the product to be taken out.

In ST5, injection is performed. The resin material measured in ameasurement process is injected to the mold construct through a passageof the injection nozzle. That is, the resin material introduced into theinjection cylinder unit of the injection apparatus and measured thereinis injected by rotation of a screw. Then, the resin material is filledinto the product cavity through the injection nozzle, a sprue of a spruebush, the resin pit, the runner and the gate. When the resin material isfilled into the product cavity, an injection speed is controlled at apredetermined speed. Further, as the product cavity is enlarged, it doesnot cause improper resin resistance with respect to a forming die, thusadvancing the injection and filling.

At this point, the resin material is stored in the resin pit as shown inFIG. 4(b). Moreover, the ultrasonic oscillator is vibratedsimultaneously with the start of supply of the resin material, therebyapplying the ultrasonic vibration to the resin material in the resin pit28 from the vibrator 25.

In ST6, the resin material is sealed in the mold. The injection nozzleis immediately closed by a nozzle shut mechanism (e.g., Japanese UtilityModel Registration No. 2040188, Japanese Patent No. 3390781). That is, anozzle shut pin is projected into the sprue to close a tip of a passageof the injection nozzle. Thus, the resin material is sealed in theforming die.

In ST7, the resin is pressurized. Compression is performed by a clampingdevice (not shown; e.g., Japanese Patent No. 3390781 mentioned above) ofthe molding machine, and the resin material sealed in the forming die iscompressed and pressurized.

The ultrasonic vibration described above preferably continues up tothese processes (ST5 to ST7). Especially, effects of the ultrasonicvibration can be promoted by using the nozzle shut mechanism.

Naturally, it is also possible to employ a method using the pressureholding instead of the nozzle shut mechanism.

That is, after a resin material M is filled into the product cavities27, 27, the mold 20 maintains a compressed state for a certain time(e.g., 60 seconds when the nozzle is shut immediately after the fillingof the resin material is completed, or 45 seconds when the pressurizedstate is maintained), and during this period, the ultrasonic vibrationpreferably continues.

In ST8, cooling is performed. For this purpose, temperature iscontrolled by a mold temperature adjustment device (not shown) so thattemperatures of parts of the forming die may be brought to apredetermined set temperature in accordance with the characteristics ofthe lens to be molded.

The resin filled in the cavity solidifies and contracts as it isgradually cooled down in the compressed state, and thus molded into apredetermined product shape.

In ST9, in a mold release process, the pressure applied onto the resinmaterial in the product cavity is reduced for a predetermined periodafter the cooling process is terminated, in a state where substantiallyconstant relative positions of the movable mold and the fixed mold aremaintained, and then the movable mold is moved from the fixed mold toopen the mold. In ST10, the mold is then opened, and the product isejected.

According to the mold 20 in this embodiment, a plurality of products canbe handled, thus providing an advantage that manufacturing efficiency ishigh.

Next, a surface treatment method for the product spectacle lens will bedescribed.

The spectacle lens is preferably subjected to a surface treatment toprovide physical and chemical durability.

Here, the surface treatment is described which is implemented for theejected product which has been subjected to gate cut processing andformed into a circular spectacle lens shape.

[Surface Treatment of the Lens]

A coat forming a surface treatment layer preferably has a coatconfiguration of a composite structure combining at least two or morekinds of a hard coat layer, an oxide covering layer (antireflectionfilm), an impact-resistant layer, a water repellent film layer, afoundation layer and the like. Normally, on a plastic lens basematerial, there is generally disposed a film configuration including theimpact-resistant layer, the hard coat layer, the oxide covering layer(antireflection film) and the water repellent film layer, or a filmconfiguration including the hard coat layer, the oxide covering layer(antireflection film) and the water repellent film layer. There is alsoa film configuration which only has the hard coat layer or which has thefoundation layer as a layer with functionality which, for example,assists in coherent properties.

A substrate material forming the hard coat layer includes acrylic-basedresin, vinyl-based resin, epoxy-based resin or the like, but anorganic-silicon-based covering layer is particularly preferable. Forexample, a coating liquid containing an organic silicon compound and/ora hydrolysate thereof indicated by the following general formula, or acoating liquid containing the organic silicon compound and/or ahydrolysate thereof and oxide fine particles indicated by the followinggeneral formula is applied and cured on the base material. (e.g.,Japanese Patent Publication Laid-open No. 3-51733, PublicationWO99/57212)R¹ _(a)R² _(b)Si(OR³)_(4-(a+b))

(where R¹, R² are alkyl, aryl, alkyl halide, aryl halide, alkenyl, or anorganic group having an epoxy group, a (meth)acrylic oxy group, amercapto group, an amino group or a cyano group whose carbon number is 1to 10, and is bonded to silicon by Si—C bonding; R³ is an alkyl group,an alkoxyalkyl group, an acyl group, a phenyl group or an allylalkylgroup whose number of carbon atoms is 1 to 8; a and b are 0, 1 or 2; anda+b is 1 or 2.)

Not only one of these kind of organic silicon compounds can be used, butalso two or more kinds of them can definitely be used together.

Furthermore, the oxide fine particles contained in the coating liquidare not particularly limited, but include, for example, silicon,antimony, titanium, aluminum, tin, tungsten, zirconium, etc. These oxidefine particles have a particle diameter of, for example, 1 to 300 nm,and are used in a form of a colloidal solution in which the fineparticles are dispersed in water, an organic solvent or a combination ofthese solvents, in order to enhance a refractive index andabrasion-resistant properties of the cure film and further to improvewater resisting properties thereof. The kinds of oxide fine particlesare preferably confected depending on a refractive index of the basematerial so that interference fringes may not emerge.

The coating liquid can further contain a curing agent to promote areaction and to cure at low temperature.

For example, specific confection of the coating liquid (whose refractiveindex is about 1.50) and a method of forming the curing covering filmare as follows.

In a glass vessel comprising agitation means, 47 pts. wt. ofγ-glycidoxypropyltrimethoxysilane, 32 pts. wt. of thermoplasticpolyurethane, 10 pts. wt. of acetic acid and 40 pts. wt. of diacetonealcohol are added, and 12 pts. wt. of 0.1 normal hydrochloric acid isdropped while agitating them. After termination of dropping, agitationis performed 24 hours, and a hydrolysate is obtained. Then, 120 pts. wt.of silica fine particles in which isopropyl alcohol is dispersed (whosesolid content is 30% and whose mean particle diameter is 15millimicron), 10 pts. wt. of acetic acid and 56 pts. wt. of diacetonealcohol are added, and agitated two hours. Subsequently, 48 pts. wt. ofpropylene glycol monomethyl ether, 24 pts. wt. of isopropyl alcohol, 5pts. wt. of aluminum acetylacetone as the curing agent, and 0.3 pts. wt.of silicone-based interfacial active agent as a lubricant are added, andare sufficiently agitated, and then matured 48 hours, thus confectingthe coating liquid.

For a coating method, a dipping method, a spin coat method and the likeare preferably used, for example.

Both a single layer and multiple layers can be used for theantireflection film, and a film configuration in which a low refractiveindex layer and a high refractive index layer are alternately laminatedcan be used for a multilayer film. The oxide covering layer of the coatis a metal oxide covering layer having a single layer or two or morelayers. Metal components constituting the oxide include, for example,aluminum, cerium, hafnium, indium, lanthanum, neodymium, antimony,scandium, silicon, tantalum, titan, yttrium, zinc, zirconium, niobium,etc., but these are not limitations.

Furthermore, the film can be formed by a vacuum deposition method, anion beam deposition method, a sputtering method, ion plating, ioncluster beam deposition, etc.

For example, specifically, SiO₂ is vacuum-deposited to a film thicknessof about 0.5μ under a pressure equal to or less than 6.7×10⁻³ Padirectly on the lens base material on which the organic silicon-basedcovering layer is formed or on the base material before covered, andabout γ/17 (γ is 550 mμ) of ZrO₂ is deposited thereon, and then SiO₂ isdeposited thereon until an optical film thickness which is the sum ofthe two substances is about γ/4. Then, γ/2 of ZrO₂ is deposited thereon,and SiO₂ is deposited thereon until it has a thickness of γ/4, therebyobtaining the plastic lens having the antireflection film which is theoxide covering layer.

The water repellent film layer is effectively and preferably formed onthe antireflection film, and for example, a silane-based compoundcontaining fluorine is dissolved into a fluorine-based solvent to obtaina water repellent thin film material, and the material is thenimpregnated into a sintered filter made of a porous material, wherebythe film is formed on a plastic optical member by vacuum depositionwhile the material is heated under manufacturing conditions including,for example, a heating temperature of 200 to 600° C., a vacuum degree ina vacuum deposition device of 1.3×10⁻¹ to 10⁻³ Pa and a deposition speedof 1×10⁻³ mg/cm² second to 1×10⁻⁵ mg/cm² second.

The impact-resistant layer is formed directly on the base material, thatis, a lower layer of the hard coat layer. For example, a thermoplasticor thermosetting polyurethane-based resin can be used for a material ofthe impact-resistant layer, and the layer is used under applicationconditions including, for example, a temperature of 100° C. to 140° C.and a thickness of about 0.05 to 8 μm on average.

[Example]

A spectacle lens was molded using the mold of the first embodiment, andeffects of the present invention were inspected. Conditions for thespectacle lens and injection molding are as follows.

Resin material: polycarbonate-based resin

Molding method: injection compression molding (molding method in thefirst embodiment)

Molding temperature: 250° C.

Spectacle lens diameter: diameter (2R)=77 mm

Spectacle lens minimum thickness: 1.4 mm

Spectacle lens power (target power): −3.84 (D)

Ultrasonic vibration frequency: 19 KHz

Ultrasonic vibration amplitude: 5 μm

Application time of the ultrasonic vibration: 60 sec

Pressure holding: 85 MPa

Time to maintain pressurized state: 45 sec

It is to be noted that the spectacle lens was injection-molded in acomparative example under the same condition as that in an example ofthe present invention except that the ultrasonic vibration was notapplied.

Results of the example of the present invention and the comparativeexample are shown in a table below.

In addition, an evaluation method is as follows.

[Strain Evaluation Method]

Visual judgment was made by a crossed-Nicol method using a straindetector manufactured by HEIDON corporation.

A judgment standard is as follows. In accordance with a view from atransmission window of the strain detector, “x” was given to one thatwas deeply colored all over to a notable degree in an area within a lenscentral radius of 35 mm, while “◯” was given to one that was notoptically colored.

[Power Evaluation Method]

Measurement was made using AL-3300 (automatic lens meter) manufacturedby HOYA.

Judgment was made so that one within ±0.125 (D) was regarded asnondefective in power and one above this value was regarded as defectivein power with reference to a target power.

It is to be noted that a lens power is generally set at a pitch of 0.25(D) for the spectacle lens, but in the present example, an optionaltarget power was set instead of setting the practical lens power, andtransfer accuracy was evaluated on the basis of deviation from thetarget power. TABLE 1 Transfer accuracy (%) Power by molding/ StrainMeasured power (D) target power Example 1 ∘ −3.80 99.0 Comp. x −3.6695.3 Example

In this way, according to the present invention, strain was reduced andthe power was improved to a great extent as compared with those inordinary injection compression molding. Thus, it was found out thatvibration pressure was applied to a resin material in a molten state ina product cavity while utilizing heating effects and pumping effectsprovided by applying the ultrasonic vibration, so that occurrence of thestrain could be effectively restrained and transferability could besignificantly improved.

While the preferred embodiments of the present invention have beendescribed, the present invention is not at all limited to theembodiments described above, and various modifications can be madewithin the scope of application of the present invention.

For example, the injection compression molding machine has beendescribed by way of example in the embodiments, but other injectionmolding machines can also be applied to the method and molding machineof the present invention.

Furthermore, in the second embodiment described above, the resin pit 28is provided at the portion coupled to the sprue 23 substantially at themidpoint between the two product cavities 27, but the resin pit 28 maybe formed into other parts as long as those parts are halfway parts ofthe runner 29.

Moreover, FIG. 6 is a perspective view showing a shape of the preferredresin pit when a nozzle shut mechanism 30 is used. In FIG. 6, the samenumerals are assigned to the same members and the same parts as those ofthe mold in the second embodiment. It is to be noted that a numeral 29 adenotes a gate portion. In this modification, for the purpose of thelens whose diameter is 77 mm in the mold of the first embodiment, theresin pit 28 is formed at a portion where the sprue 23 is coupled to therunner 29, and the preferably used resin pit 28 has a pseudo-circularportion whose diameter is 20 mm to 40 mm and whose thickness is 2 mm to4 mm.

Next, another preferable resin pit has a shape substantially similar tothat in FIG. 6, but it has sizes including a diameter of 50φ, acurvature of about 50 R and a thickness of 2 mm to 4 mm, and comprises acurved upper surface. In this case, the pumping effects are better withthe curved shape than with a planar shape.

INDUSTRIAL APPLICABILITY

The present invention can be effectively utilized in various fields ofoptical lens by providing, for example, a spectacle lens to enable atechnical improvement, and in particular, the present invention can beeffectively utilized in fields of spectacle lenses.

1. A molding method using ultrasonic vibration in which a resin materialin a molten state is filled into a cavity of a mold and cooled down toobtain a product in a predetermined shape, the method beingcharacterized by: preparing the mold having a product cavity to mold theproduct, a dummy cavity to mold a dummy product, and a runner by whichthe product cavity and the dummy cavity are connected; filling the resinmaterial into the product cavity and supplying the resin material in themolten state to at least part of the dummy cavity; and applying theultrasonic vibration to the resin material in the dummy cavity atpredetermined timing.
 2. A molding method using ultrasonic vibration inwhich a resin material in a molten state is filled into a cavity of amold and cooled down to mold a product in a predetermined shape, themethod being characterized by: preparing the mold having a plurality ofproduct cavities to mold the products, a runner by which the productcavities are connected to each other, and a resin pit provided at ahalfway part of the runner; supplying the resin material to the resinpit and filling the resin material into all of the plurality of productcavities; and applying the ultrasonic vibration to the resin material inthe resin pit at predetermined timing.
 3. The molding method using theultrasonic vibration according to claim 1, characterized in that thepredetermined timing is after start of supply of the resin material toat least part of the dummy cavity or the resin pit and while the resinmaterial in the runner has a predetermined viscosity.
 4. The moldingmethod using the ultrasonic vibration according to claim 1,characterized in that the ultrasonic vibration is applied while acompressed state is maintained after the resin material is filled intothe product cavity and compressed.
 5. The molding method using theultrasonic vibration according to claim 1, characterized in that theultrasonic vibration is applied so that an amount of the resin materialflowing into the product cavity from the dummy cavity and air gaps otherthan the product cavity is in a range of 0.1% by volume to 5% by volumeof the resin material filled into the product cavity.
 6. The moldingmethod using the ultrasonic vibration according to claim 1,characterized in that the ultrasonic vibration is applied immediatelyafter the filling of the resin material is started and until a gate incommunication with the product cavity is sealed.
 7. The molding methodusing the ultrasonic vibration according to claim 1, characterized inthat a nozzle of a molding machine to supply the resin material to themold is closed immediately after the filling of the resin material iscompleted.
 8. The molding method using the ultrasonic vibrationaccording to claim 7, wherein the product is an optical lens.
 9. Themolding method using the ultrasonic vibration according to claim 7,characterized in that the optical lens is a spectacle lens, and a stepof subjecting the obtained spectacle lens to a surface treatment isfurther added.
 10. An optical lens characterized by being manufacturedby a molding method according to claim
 8. 11. A molding machine in whicha resin material is filled into a cavity formed in a mold and compressedto mold a product in a predetermined shape, the molding machine beingcharacterized by comprising: the mold having a product cavity to moldthe product, a dummy cavity to mold a dummy product, and a runner bywhich the product cavity and the dummy cavity are connected; ultrasonicwave application means for applying ultrasonic vibration to the resinmaterial in the dummy cavity; and control means for controllingapplication timing of the ultrasonic vibration by the ultrasonic waveapplication means.
 12. A molding machine in which a resin material intoa cavity formed in a mold and compressed to mold a product in apredetermined shape, the molding machine being characterized bycomprising: the mold having a plurality of product cavities to mold theproducts, a runner by which the product cavities are connected to eachother, and a resin pit provided at a halfway part of the runner;ultrasonic wave application means for applying ultrasonic vibration tothe resin material in the resin pit; and control means for controllingapplication timing of the ultrasonic vibration by the ultrasonic waveapplication means.
 13. The molding machine according to claim 11,characterized in that timing when the control means applies theultrasonic vibration is after start of supply of the resin material toat least part of the dummy cavity or the resin pit and while the resinmaterial in the runner has a predetermined viscosity.
 14. The moldingmachine according to claim 11, characterized in that the timing when thecontrol means applies the ultrasonic vibration is while a compressedstate is maintained after the resin material is filled into the productcavity and compressed.
 15. The molding machine according to claim 11,characterized in that the mold has a sprue in communication with therunner in addition to the runner.
 16. The molding machine according toclaim 11, characterized in that the resin pit located at a midpoint ofthe runner.
 17. The molding machine according to claim 11 any, whereinthe product is an optical lens.
 18. The molding machine according toclaim 12, characterized in that timing when the control means appliesthe ultrasonic vibration is after start of supply of the resin materialto at least part of the dummy cavity or the resin pit and while theresin material in the runner has a predetermined viscosity.